Signal-amplitude responsive circuit



2 Sheets-Sheet l +mmmm H C m 73 Iii C. C. SHUMARD SIGNAL-AMPLITUDE RESPONSIVE CIRCUIT INVENTOR. CHARLES C. SHUMARD ATTORNEY //VPU7' Feb. 19, 1957 Filed Dec. 51, 1953 Feb. 19, 1957 c, c, SHUMARD 2,782,373

SIGNAL-AMPLITUDE RESPONSIVEI CIRCUIT Filed Dec. 31', 1953 2 Sheets-Sheet 2 INVENTOR.

ATTORNEY United States Brent 9 a SIGNAL-A'M'BIJITUDE RESPONSIVE-CTRCUI'D Charles C; Shumardi Hopewell, L assignor to Radio Corporationof A'merica,,a corporation of Delaware Application December-31, 19 53, Serial-N; 401,669 6 Claiins. c1; 332 -11) This invention rela-tes to electrical translation systems for electrical signals of l varying: amplitude and particu-' la'rly: to 'clect-ronic-circuits for classifying or'quanti-zing in=accordance withits amplitude:

Quantizinga circuitsim the computer fieldare sometimes used to' conv"ert-signals in analogue forrn'to'a digital forms" For example, the reading; of an instrument in the form "of a voltage of=varyingianiplitude may 'be con ver-ted to a signal on one of a plurality-of channels: in accordance with the voltage amplitude. Different'switch ing operations may? be initiateddepending upon the channel-- to: which the signal is applied: Quantizingcit cuits=are described in -Ua S; Patents Nos;'2 ,4-86,390, and 2,541,039:

In 'sorne applications of a quantizing;circuit, it is' desir able that there be a backlash or hy'stereSis ope-rational characteristicioli' the-circuit; That is; as the circuit inpu-t voltage-increases-through: discrete 'levelsg the signal-"is applied success'ivel-y to the output channelsin'a prcde= termir'ied I order; and as the voltage' decre'ases through the same: or overlapping v'oltagelevels; the signal is applied to the next-higher order channels. A circuit having a backlash characteristic may; be used where there is feedbacle control-of the input in ac'cordance with the discreteoutputcha-nnel selected." By; means of the backlash characteristic and a feedback network, it ispossible== to providean interpolation betweentwo' discrete output channels for a voltage that'lies betweemthe-twocorre spending? levelsz- The article A high-accuracy timedivision 1 multiplier by: E A; Goldberg-, RGA= Review, September 19-52, pp.- 265-274;describesafeedback circuit in which interpolation is :achieved by/rrieans of a-flip flop circui-t that is ammo-position qttantizi'ngcircuit having a backlash characteristic: bac'klasla' quantizin circuitha'vingimore than twopositions is described in the c'opending patent application of E. A1 Goldbe'rg;-. entitled Signal-Amplitude Responsive Circiiitg Sarial No; 401-;682; filed concurreutlyfiherev'lith'a An object-of this inven'tion is to provide a new and improved-circuit forprovi'din'g a signal on-one of a pinrality of outputs-in accordance with the amplitude of I avarying voltage: I

Another o'bject: of this invention is to rovide an iniproved and simple circuifithat a'ssurne's'a plurality of different states in accordancc with amplitude variations of a direct voltage:

Another object of' this" invention is and i accnrate circuit #havi'n'g' a bat lash characteristic l for quantiZi-ng I a: varying zelectrical Sig-na l in accordanee with sisto'rs and separate output terminals are connected to each tube anode-. The tubegrids: are cemiected' tn' altl" to providr'e a reliable 2,782,373 Patented Feb. 19, 1957 input terminal through separate grid resistors and separate input resistorsin seriesi An input resistor is not needed forthe last tube. The input resisto'rsdecrease in magnitude from'the first to'thepenultimate tube: Connected to the 'junctionsotthe-grid and inputresi'stors-are separatediode limiter circuits. Tliediode limiters prevent the junction voltages from rising above that required to bias the tubesto full conduction.

At the low-extrerneofthe input voltage range, all the tubes are biased'to cut-oft condition throughth'e voltagedivider biasing system formed'by the load, coupling,- grid and input resistors. The tube grids are biasedmore negatively from the first to'the last inamou'nts equal to'the different voltage drops across-the different magnitude input resistors. As theinput voltage increasesthrough steps-equal'to'the difieren'cescf the inputresistor voltage drops; the tubes are suc'cessiVelybiasedto-conduction fromthe first to: the last. Whenthe second tube con ducts; the lowered anodevoltage is' applied through a coupling resistor to the first tube'grid and regeneratively biases-the first" tube to cutofi. Similarly, whenthe succeeding tubesconduct; all of the preceding tubes in order are cutoff: On1y-one-tube conducts at'a' time; and the anode-voltageof theconductin'g' tube islowwhile the others'are' highr Thus, only one" output termi'n-al'is at a low voltage'and th'e -ot-he'rsare' at ahighvol-tage. The orderof the' low voltageterminal is related to theinput voltageampl-itude', anti-thelow voltage signal may be used for controlpurposes;

Whentheinputvo-ltagedecreases; the tubesare suc-' ces 'vely "biased 'to -cutofi in re'verse order; When a tube is" conducting; its-grid voltage is at a relatively more positive value -due-to thehi'gh-anode voltages of all the other non-conducting"tubesthat' a-reapplied through the coupling resistors. Whe-n a-tub'e is-cut ofi and theprecedi'n'gtube is condue-ting the non-conducting tube grid isat a relatively mo re" negative voltage due to the low anode" voltageof the preceding conducting tube. Consequently, the increasing input'v'olta-geat'which it is cut off; Thus there is bacltlash inthe operation of the circuit. The backlash characteristic may" be made relatlve'ly large or negligible-dependin'g on the relative magnitudes: of the coupling andother-biasing resistors.

The foregoing anti o'ther objects; the-advantages and novel features -of this invention, as well as'the invention itself, both as to its orgailiz-ation and mode of-operation; may be best unders'tood wh'en readtogether with the accompanying drawing in which like reference numerals refer to Iike part'S" and in which a Figure 1 is aschematic-"circuit diagram of an embodimentof this inventiong and Figure 2 is aschematic circuit diagram-illustrating a modificationof the embodiment shown in Figure 1.

Referring toFigul-e' 1, aquantizing'circuit in accordance"with-thisinvention has a-plurality of stages 10, 12, 14-,1'6, each including a grid-controllecl electron tube 18, 20, 22 24; Four 'stagesare shown in'Fig'ure 1 forsimplicity'of illustration. However,the invention may be applied to a greater or lesser number of stages where desired. The-anode of each-tubc-18'-24 is coupled to thegrids of all'the: other tubes through three separate coupling resistors 26; 28;- 30. The control grid of each tube 18-44 is" connected through: aseparate first grid resistor 32 to ground; The cathodeof each tube 1'8-24 or inputs for theassociated tube grids.- The rid of the" fourth tube 24 is connected through its second grid resistor 34 directly to the input terminal 42 which is the biasing point for that tube 24. The junctions 44, 46, 48 f the second grid resistors 34 and input resistors 36, 38 and 40 are connected, respectively, to the anodes of three separate diode limiter tubes 50, 52, 54. The diode 50, 52, 54 cathodes are connected to a negative direct voltage, -100 volts. The tube anodes are connected through separate anode loads 56 to a source of operating potential, +300 volts. Each anode load 56 is made up of two different resistors 56a, 56b in series. Each junction of the two resistors 56a, 56b is connected to a separate output terminal 58, 60, 62, 64. The input voltage source may be a D. C. amplifier 66.

The coupling resistors 26, 28, 30 from the first tube 18 anode to the grids of the succeeding tubes vary in magnitude, the first or largest resistor 26 being connected to the second tube 20 grid, the second or intermediate magnitude resistor 28 to the third tube 22 grid, and the third or smallest resistor 30 to the fourth tube 24 grid. The magnitudes of the first, second and third coupling resistors 26, 28, 30 from the second tube 20 anode are the same as the corresponding ones from the first tube 18 anode, with the first resistor 26 connected to the third tube 14 grid, the second resistor 28 to the fourth tube 24 grid, and the third resistor 28 to the first tube 18 grid. The three coupling resistors 26, 28, 30 from each of the anodes of the third and fourth tubes 22, 24 have corresponding magnitudes and are arranged in the same manner. Thus, there is a symmetrical coupling resistor network to each tube grid made up of a first, a second, and a third resistor 26, 28, 30, each such resistor being connected to a separate one of the three other tube anodes. The first input resistor 36 to the first tube 18 grid is largest in magnitude, the second resistor 38 is intermediate in value, and the third resistor 40 is smallest in value. The load resistors 56, coupling resistors 26, 30, grid resistors 32, 34, and input resistors 36, 40 form a voltage-dividing biasing network.

In operation, at the low extreme of the input voltage range, 120 volts for the specific component values shown in Figure l, the voltages at the difierent biasing points 44, 46, 48, 42 are respectively -10S, 110, -1l5, and --l20 due to the voltage drops across the three input resistors 36, 38, 40. All the tubes 1824 are biased to cutoff by the above biasing point voltages. When the voltage at each of the biasing points 4248 increases to -l00 volts, the associated tube grid is at approximately zero bias and the tube conducts. As the input voltage increases, becoming less negative, the first tube 18 conducts. A further input voltage increase results in the second tube 20 conducting, and a simultaneous rapid cutoff of the first tube 18. As the voltage continues to rise to the high extreme of its range, the third and fourth tubes 22, 24 are successively rendered conductive and all the preceding tubes cut off. As the voltage decreases from the high range extreme, there is a reversal in the order of conduction of the tubes from the fourth tube 24 to the first tube 18, and the final non-conduction of all of them. Only one tube conducts at a time. Therefore, the junctions of the conducting tube anode resistors 56a, 56b and the corresponding output terminal 58-64 are at a low potential, while all the other output terminals are at a high potential. This low voltage output signal is directly related to the input voltage amplitude and may be used for control purposes. Where it is desired that the output signal be a high voltage, a separate inverter amplifier stage (not shown) may be connected to each output. terminal.

When the input voltage increases to a level at which the second tube 25) biasing point 46 voltage is the triggering-on voltage of -l00 volts, the first biasing point 44 is held at l00 volts due to conduction in the first limiter diode t). There is zero bias on the second tube 20 grid so that the second tube 20 starts to conduct. The resulting fall in the second tube 20 anode potential is applied to the first tube 18 grid through the third coupling resistor 30, tending to cut that tube off. The resulting rise in the first tube 18 anode potential is regeneratively applied to the second tube 20 grid. The action continues until the second tube is conducting and the first tube 18 is cut off. The second tube 20 third coupling resistor 30 is smaller than the third tube 22 second coupling resistor 28 and the fourth tube 24 first coupling resistor 26. Therefore, the voltage division to the first tube 18 grid from the low-potential second tube 20 anode and the high-potential third and fourth tube 22, 24 anodes, as well as the limiting action of the first diode 50, permit a relatively small second tube 20 anode swing to cut off the first tube 18. In a similar manner, when the input voltage increases sufliciently to bring the third tube biasing point 48 to the triggering-on voltage of volts, the third tube 22 conducts, cutting otf the second tube 20 through the third tube 22 third coupling resistor 30 and holding the first tube 18 cut off through the third tube 22 second coupling resistor 28. When the input voltage increases to 100 volts, the fourth biasing point 42 is at the triggering-on voltage. The fourth tube 24 conducts, and the preceding tubes 18, 22 are cut off because of the bias supplied by the fourth tube 24 and the action of the limiting diodes 50, 52, 54. All the tubes, except the first tube 18, are regeneratively triggered on as the input voltage increases.

When the input voltage decreases from -100 volts, becoming more negative, the tubes 18--24 are rendered conductive sequentially in the reverse direction. All the tubes, except the first tube 18, are regeneratively triggered off as the input voltage becomes more negative. Considering the condition of the circuit with the input voltages at -100 volts, the fourth tube is conducting, and the other tubes are cut off. As the input voltage decreases, becoming more negative, the bias on the grids of the first, second and third tubes 18, 20, 24 remains at cutoff, due to the limiting diodes 50-54 and the bias supplied by the fourth tube 24 anode. When a value of the input voltage is reached at which the fourth tube starts to cut otf, the fourth tube 24 anode does not supply enough bias to keep the third tube 22 non-conducting. Therefore, the third tube 22 starts to conduct, supplying the additional cutoif bias to the first and second tubes 18, 20 formerly supplied by the fourth tube 24. The third tube 22 also regeneratively cuts off the fourth tube 24. The same process is repeated for the other tubes 18, 20 as the input voltage becomes more negative, execpt that the cutoff of the first tube 18 is not regenerative.

The biasing point 46, 48, 42 voltage for triggering off all the tubes, except the first tube 18, when the input voltage is decreasing, is somewhat more negative than the biasing point voltage for triggering on the same tube when the input voltage is increasing. For example, when the third tube 22 is conducting, its anode is at a relatively low potential which tends to bias the fourth tube 24 grid to a relatively low voltage. When the fourth tube 24 is the only one conducting, all the other tube 18, 22 anodes are at a relatively high potential which tends to bias the fourth tube 24 grid to a relatively high voltage. Thus, the fourth tube 24 grid tends to be biased less negatively by the third tube 22 anode potential when the fourth tube 24 conducts and more negatively when the third tube 22 conducts. Consequently, the biasing point 42 voltage necessary to trigger olf the fourth tube 24 is more negative than that which triggers on the fourth tube 24. The backlash between the triggering-on and triggering-off voltages is also characteristic of the third and second tubes 22, 20. However, there is no backlash in the first tube 18 trigger voltages, in the circuit shown in Figure 1, because the second, third and fourth tubes 20, 22, 24 are cut off for both first tube 18 conditions. The backlash characteristic of the circuit depends on the relative magnitudes ofthe coupling andothenbiasingtnetwork resistors. By appropriatechoice of resistor values, the amount of backlash may be made large or negligible.

The. input voltage steps for producing triggering-on upotentials at successive biasingpointsrt t, 46, 48, 42 are --:substantially equalfor equal stepszin"inputa'resistor 36,

'38, 40 magnitudes.

The relatively- ,small values'zof "the different magnitude input resistors do not materially affect the substantially equal currents flowing in the corresponding, symmetrical, biasing network sections. The magnitude of the input voltage steps may be made large or small by appropriate choice of input resistor 36, 38, 40 magnitudes.

Additional stages (not shown) may be added to circuit, as desired. Each additional stage would have the same form as those shown in Figure l. The specific component values given in Figure 1 are illustrative and are not to be construed as a limitation on the scope of the invention. The tube types are: triodes, /2 6847; diodes, /2 6AL5. Corresponding components in each stage have the same parameters except where values are otherwise given.

In Figure 2, :a modified circuit embodying this invention is shown. The first tube 18 is connected in a bistable multivibrator or flip-flop circuit with an additional grid-controlled tube 70. The first tube 18 anode is connected through a coupling resistor 72 to the additional tube 70 grid. The additional tube 70 anode is connected through a coupling resistor 74 to the first tube 18 grid. The additional tube 70 grid is connected through first and second grid resistors 76, 78, respectively, to ground and the -l00 volt source. The additional tube 70 anode is connected to the +300 volt source through an anode resistor 80. The circuit shown in Figure 2 is otherwise the same as that of Figure l, and the other tubes 20, 22, 24 are omitted for simplicity of illustration.

When the input voltage is at the negative extreme, about l20 volts, the biasing point 42-48 voltages are all below the triggering-on potential of -100 volts. Therefore, the first, second, third, and fourth tubes 18-44 are cut off. The additional tube 70 second grid resistor 78 is connected to the negative source at the triggering-on potential, -100 volts. Therefore, the additional tube 70 is conducting. When the first biasing point 44 voltage rises to 100 volts, the first tube 18 conducts and cuts off the additional tube 70 regeneratively. Similarly, for a decreasing input voltage, the first tube 18 is regeneratively cut 011 in the same manner as the other tubes 2t), 24. Because the additional tube 70 anode potential is relatively low when that tube 70 conducts, there is a backlash between the first tube 18 triggering-on and triggering-off potential.

It is evident from the above description of this invention that a simple and reliable quantizing circuit is provided that has a backlash characteristic or not as desired. A large or a small number of stages may be employed with a relatively small number of components.

What is claimed is:

1. A circuit that assumes at least three different states in accordance with amplitude variations of an input voltage, said circuit comprising at least three voltage responsive electron control devices arranged in a predetermined operational order, each of said control devices having anode, cathode and control electrodes and conductive and non-conductive operating conditions, separate impedance means coupling each of said device anodes to said control electrode of each of the others of said devices, separate input terminals coupled to said control electrodes, and input means for applying a different voltage to each of said input terminals in accordance with the amplitude of said input voltage to bias said control devices in said order to one of said operating conditions as said input voltage varies in one direction and in the 1A4 circuit'iaccordingr r to clai'm: lswherein said input anneansincludes. meanstoralimiting the. voltages atasaid input-terminals.

3. ,A circuit-accordingtorlelaimalxwhereinieachnf. said separate coupling;timpedanceimeans includes arresistor, at least one of said resistors from each of said control device anodes having a different magnitude than the others, said different magnitude resistors being connected to said control grids of succeeding order control devices, and said input means includes a plurality of different magnitude resistors respectively connected to different ones of said input terminals, and separate limiting diodes connected to said input terminals.

4. A circuit that assumes at least three different states in accordance with amplitude variations of an input voltage, said circuit comprising at least three voltage responsive electron control devices each having two conditions of operation and an input terminal, means for biasing each of said control devices to change from one operating condition to the other upon the application of a first predetermined voltage and to change from said other to said one operating condition upon the application of a second predetermined voltage substantially different from said first voltage, and input means for applying dilferent voltages to said input terminals in accordance with said input voltage, said input means including means for limiting the amplitude of the voltages applied to said input terminals.

5. A circuit that assumes at least three dilferent states in accordance with amplitude variations of an input voltage, said circuit comprising at least three voltage responsive electron control devices arranged in a predetermined operational order, each of said control devices having conductive and non-conductive operating conditions and including anode, cathode and control electrodes, separate input terminals coupled to said control electrodes, means for biasing each of said control devices to change from one of said operating conditions to the other upon the application of a first predetermined voltage to the associated input terminal and to change from said other to said one operating condition upon the application of a second predetermined voltage substantially dilierent from said first voltage, said biasing means including separate resistors coupling each of said device anodes to said control electrode of each of the others of said devices, at least some of said resistors coupled to each anode being different in magnitude than the others, all of said difierent magnitude resistors being coupled in a symmetrical arrangement, and input means for applying voltages to said input terminals in accordance with said input voltage, said input means including a plurality of different magnitude resistors respectively connected to different ones of said input terminals, and separate limiting diodes connected to said input terminals.

6. A circuit that assumes at least three different states in accordance with amplitude variations of an input voltage, said circuit comprising at least three electron discharge tubes arranged in an operational order from a first one of said tubes to a last one of said tubes, each of said tubes having an anode, cathode and control grid, separate different magnitude resistors coupling the anode of each of said tubes to said control grid of each of the other tubes, said resistors from the anode of said first tube decreasing in magnitude with the order of the tube to the control grid of which it is coupled, each of the pluralities of resistors from the anodes of said other tubes decreasing in magnitude with the order of the tube to the control grid of which each resistor is coupled, said order being cyclical continuing from said last tube back to said first tube to provide a symmetrical coupling resistor network, a common input terminal, separate means coupling said common input terminal to said control References Cited in the file of this patent grids, each of said separate means for at least said first UNITED STATES PATENTS and second control gr ds lncludmg a different magnitude input resistor connected at one end to said common 2,541,039 Cole Feb. 13, 1951 input terminal, separate limiting diodes connected to 5 2,589,465 Weiner Mar. 18, 1952 the other ends of said input resistors, and separate out- 2,594,092 Taylor Apr. 22, 1952 put terminals connected to said anodes. 2,612,550 Jacobi Sept. 30, 1952 

